Polyimide resin is insoluble and infusible resin that has a super high thermal resistance, and has excellent properties, such as a thermally-oxidation resistance, a thermal resistance property, a radiation resistance, a low temperature property, a chemical resistance, and the like. Therefore, the polyimide resin is being used in wide fields, such as thermal resistance state-of-the-art materials, for example materials for automobile, materials for flight, materials for spacecraft, and the like, and electronic materials, for example an insulation coating, an insulation film, a semiconductor, an electrode protective film of TFT-LCD, and the like, and also is being recently used in a transparent electrode film, and the like by coating on a surface or containing a conductive filler in a film and display material, such as an optical fiber or a liquid crystal alignment film.
However, a general polyimide resin has turned brown or yellow due to high density of aromatic ring so that it has low transmittance in a visible ray region and is a color that is associated with yellow so that makes optical transmittance to be decreased. Therefore, the general polyimide resin is difficult to use in the field that needs transparency.
Therefore, various efforts are being performed in order to improve a color and transmittance of a general polyimide film, but the thermal resistance seems to be decreased in proportion to the improvement of the color and the transmittance of the film.
In addition, the supply of a transparent film having high thermal resistance is required in addition to a diversification of the function in the use for various electric-electronic materials that are applied with the polyimide film.